Java - 格式化双倍值作为美元金额

Question

我需要将双"amt"格式化为美元金额println("$"+美元+"."+美分),以便小数点后有两位数.

这样做的最佳方法是什么？

if (payOrCharge <= 1)
{
    System.out.println("Please enter the payment amount:");
    double amt = keyboard.nextDouble();
    cOne.makePayment(amt);
    System.out.println("-------------------------------");
    System.out.println("The original balance is " + cardBalance + ".");
    System.out.println("You made a payment in the amount of " + amt + ".");
    System.out.println("The new balance is " + (cardBalance - amt) + ".");
}
else if (payOrCharge >= 2)
{
    System.out.println("Please enter the charged amount:");
    double amt = keyboard.nextDouble();
    cOne.addCharge(amt);
    System.out.println("-------------------------------");
    System.out.println("The original balance is $" + cardBalance + ".");
    System.out.println("You added a charge in the amount of " + amt + ".");
    System.out.println("The new balance is " + (cardBalance + amt) + ".");
}

Answer 1

使用NumberFormat.getCurrencyInstance():

double amt = 123.456;    

NumberFormat formatter = NumberFormat.getCurrencyInstance();
System.out.println(formatter.format(amt));

输出:

$123.46

Answer 2

用于DecimalFormat以所需格式打印十进制值,例如

DecimalFormat dFormat = new DecimalFormat("#.00");
System.out.println("$" + dFormat.format(amt));

如果您希望以美国数字格式显示$ amount,请尝试:

DecimalFormat dFormat = new DecimalFormat("####,###,###.00");
System.out.println("$" + dFormat.format(amt));

使用时.00,它总是打印两个小数点而不管它们的存在.如果只想在它们存在时打印十进制,则使用.##格式字符串.

Answer 3

您可以使用DecimalFormat

DecimalFormat df = new DecimalFormat("0.00");
System.out.println(df.format(amt));

这将为您提供始终2dp的打印输出.

但实际上,由于浮点问题,你应该使用BigDecimal来赚钱

Answer 4

您可以将 printf 用于单衬

System.out.printf("The original balance is $%.2f.%n", cardBalance);

这将始终打印两位小数，根据需要四舍五入。